|Publication number||US7062239 B2|
|Application number||US 10/114,114|
|Publication date||Jun 13, 2006|
|Filing date||Apr 3, 2002|
|Priority date||Jan 9, 2002|
|Also published as||US20030129952|
|Publication number||10114114, 114114, US 7062239 B2, US 7062239B2, US-B2-7062239, US7062239 B2, US7062239B2|
|Original Assignee||Mitsubishi Denki Kabushiki Kaisha|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (17), Referenced by (8), Classifications (16), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to an on-vehicle equipment provided on a side of a vehicle in dedicated short-range communication in intelligent transport system, in particular, an on-vehicle equipment which can firmly fix a desirable receive channel with high efficiency.
2. Description of Background Art
Intelligent transport system (hereinbelow referred to as ITS) is to transmit and receive various data by communication between an on-road equipment provided on a side of road and an on-vehicle equipment provided on a side of vehicle in use of dedicated short-range communication (hereinbelow referred to as DSRC) for communicating only within a limited range on a road utilizing a radio wave in the microwave band.
In ITS, an electronic toll collection system (hereinbelow referred to as ETC) is included. It is a system for automatically collecting toll without stopping vehicles. The system enables an automatic toll payment procedure in use of the above-mentioned DSRC without temporarily stopping a vehicle when the vehicle passes through a tollgate in an expressway. In ETC, an on-vehicle equipment on the vehicle side communicates with on-road equipments, respectively provided in tollgates. Two frequencies F1 and F2 are alternately allocated to adjacent gates to avoid interference between the frequencies. These two frequencies F1 and F2 and a communication method are determined by the standard of DSRC.
According to DSRC, for example, a vehicle approaching a toll gate alternately switching over between the frequencies F1 and F2 as a local frequency because it is unknown whether the frequency of the toll gate is F1 or F2. The vehicle receives data, and selects the frequency by fixing the frequency when the data are normally received.
Next, an operation will be described.
If the timer 8 is judged to be effective in Step S41, it is judged whether or not a radio wave sent out of the on-road equipment is normally received in Step S44. If the radio wave is normally received, in Step S45, the received frequency is determined. In Step S46, the received F1/F2 signal is outputted. In Step S47, the received F1/F2 signal is compared with the selected F1/F2 signal selected in Step S42. In Step S48, when the received F1/F2 signal is the same as the selected F1/F2 signal, a local frequency outputted from the PLL oscillating unit 6 is fixed. In Step S49, if the received F1/F2 signal is different from the selected F1/F2 signal, the local frequency outputted from the PLL oscillating unit 6 is switched over.
In the conventional DSRC of ITS, only ETC is available, whereby the two frequencies of the above-described two channels of F1 and F2 are used. However, in recent years, various applications to, for example, collection of charges in gas stations and drive-through shops and traffic information service are planned besides ETC. Accordingly, seven frequencies (seven channels) are allowed to use in accordance with the DSRC standard.
In the conventional on-vehicle equipment for DSRC, there is no measure to distinguish a frequency used in a communication area and it is impossible to select the frequency until a vehicle approaches to the communication area as described above. Therefore, the two frequencies are switched over by a predetermined time in order to select one. However, when the system is applied to an on-vehicle equipment for DSRC using all applications other than ETC, it is necessary to select the seven frequencies by an equal time period, whereby there is a problem that a substantially long time is required to select the frequencies.
As shown in
Accordingly, when the conventional technique is applied to ITS using seven frequencies described above, it is necessary to provide a frequency search time utmost about 49 ms. Therefore, there are problems that the search time becomes very long and the ETC standard requiring that the frequency be completely selected within nine frames, i.e. about 21.1 mS, is not satisfied.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an on-vehicle equipment for DSRC in ITS, which certainly fixes as a predetermined frequency with high efficiency.
According to a first aspect of the present invention, there is provided an on-vehicle equipment for Dedicated Short-Range Communication (DSRC) in Intelligent Transport System (ITS) including: a receiving antenna for receiving radio waves sent out of on-road equipments; a frequency converting unit for converting the frequencies to signals of a predetermined frequencies in a plurality of local frequencies; a channel selecting filter unit for taking only a predetermined channel out of the signal obtained in the frequency converting unit; a demodulator for digitizing an output from the channel selecting filter unit; a normal reception determining unit for judging whether or not the radio wave is normally received based on an output from the demodulator; a PLL oscillating unit for outputting the local frequencies to the frequency converting unit; and a frequency switching determining means for outputting a selected frequency signal by sequentially switching the local frequencies at a predetermined cycle in accordance with a preset priority sequence of switching the local frequencies in correspondence with types of the on-road equipments, whereby a desirable communication frequency can be certainly fixed with high efficiency even though the number of frequencies to be selected is large.
According to a second aspect of the present invention, there is provided the on-vehicle equipment for DSRC in ITS, wherein the frequency switching determining means is set so as to highly frequently select a frequency of high priority, whereby a desirable communication frequency can be certainly fixed with high efficiency even though the number of frequencies to be selected is large.
According to a third aspect of the present invention, there is provided the on-vehicle equipment for DSRC in ITS, wherein the frequency switching determining means determines the priority sequence of the frequencies based on the vehicle speed, whereby a desirable communication frequency can be fixed with high efficiency even though the number of frequencies to be selected is large.
According to a fourth aspect of the present invention, there is provided the on-vehicle equipment for DSRC in ITS, wherein the frequency switching determining means is operated under a first control mode of selecting only a frequency or frequencies of high priority and a second control mode of selecting at least a frequency of low priority, and the first control mode is transferred to the second control mode when a switching command is externally inputted, whereby a communication frequency required by the driver can be quickly selected.
According to a fifth aspect of the present invention, there is provided the on-vehicle equipment for DSRC in ITS, wherein the frequency switching determining means returns from the second control mode to the first control mode after a lapse of a predetermined time period from the transfer from the first control mode to the second control mode, whereby the second control mode of selecting the frequencies of low priority is quickly returned to the first control mode of selecting the frequencies of high priority after a lapse of a predetermined time, whereby erroneous selection of the frequencies of high priority can be prevented.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
A detailed explanation will be given of preferred embodiments of the present invention in reference to
Further, Frequencies f3 and f4 used in Advanced Cruise-Assistant Highway System-Information (hereinbelow referred to as AHS-i) for providing information shower such as traffic information, guide of curve, and information of road condition, in which certainty is not required in comparison with ETC though the information and the guide are received during high-speed run.
Further, in logistic control for controlling destinations of vehicles, senders, specifications of packs, and so on by communicating with entering and dispatching vehicles through an on-road equipment located at around a garage of freight company, radio waves are received under a situation that a speed of vehicle is relatively low for entering and dispatching. Frequencies f5 and f6 used therefore are in a priority sequence of 3.
Further, Frequency f7 used to receive payment in drive-through shops, gas stations, and so on where problems are not caused even though the frequency select time is relatively long is in the lowest priority sequence of 4 because radio waves are received in a state that a vehicle substantially stops.
Because in all of Step 1 through Step 15, Frequencies f1 and f2 are set in the first priority, chances that the frequencies of the highest priority are selected increase. Further, because the second priority through the fourth priority are selected in a part of the steps, chances that the second through fourth priorities are selected are lower than that in the first priority, and the chances that the second priority, the third priority, and the fourth priority are selected decrease in this order.
Next, an operation will be described.
When the timer 8 is judged to be effective in Step S1, it is judged whether or not the radio wave sent out of the on-road equipment is normally received in Step S4. If the radio wave is normally received, the received frequency is judged among the frequencies f1 through f7 in Step S5. In Step S6, the received f1/f7 signals are outputted. In Step S7, the received f1/f7 signals are compared with the selected f1/f7 signals selected in Step S2. If the received signal is the same as the selection signal, the local frequency outputted from the PLL oscillating unit 6 is fixed in Step S8. If the received signal is different from the selected signal, the frequency outputted from the PLL oscillating unit 6 is switched in Step S9.
As described, according to Embodiment 1, because the frequencies of high priority are frequently selected even though the number of frequencies to be selected is large, it is possible to certainly fix a desirable communication frequency with high efficiency in comparison with the conventional technique of evenly selecting all of the frequencies. Further, when the priority sequence of the frequency used for ETC is set to be the highest, this frequency is very often selected, and it is possible to satisfy the above-described standard of ETC by completing to select the frequency within nine frames.
This embodiment of using DSRC illustrating in
In Step S22, if the external switch 10 is not turned on in Step S21, it is judged whether or not the first timer 8 a is effective. If it is effective, it is judged whether or not a radio wave sent out of an on-road equipment is normally received in Step S25. If the radio wave is normally received in Step S30, a routine of fixing or switching frequency in Steps S5 through S9 in
On the other hand, if the first timer 8 a is judged not to be effective in Step S22, frequencies of high priority, for example frequencies f1 and f2, are selected and the selected frequency is outputted as a selected f1/f7 signals in Step S23. In Step S24, the timer 8 a is set.
Further, in Step S26, if the external switch 10 is turned on in Step S21, the second timer 8 b is set. In Step S27, it is judged whether or not the second timer 8 b is effective. If the second timer is judged to be effective, a frequency of low priority, e.g. frequencies other than the frequencies f1 and f2 is selected, and the selected frequency is outputted as the selected f1/f7 signals in Step S28. In Step S29, it is judged whether or not the radio wave sent out of the on-road equipment is normally received. If it is normally received, in Step S30, a routine of fixing or switching frequency in Steps S5 through S9 is performed as in
As described, according to Embodiment 2, when it is previously known that a vehicle reaches a location of an on-road equipment sending out a frequency of low priority, e.g. drive-through shop and gas station, the control modes are changed over by the external switch 10, whereby an effect of quickly selecting a frequency required by a driver is obtainable.
Although, in Embodiment 2, f1 and f2 are provisionally exemplified as the frequency of high priority, and the frequencies other than f1 and f2 are provisionally exemplified as the frequency of low priority, it is possible to arbitrarily set the frequencies of high priority to be f1 through f4 and the frequencies of low priority to be f5 through f7, whereby it is needless to say that a similar effect is obtainable.
As illustrated in
Although, in the above-described embodiments, the frequencies are from f1 through f7 as much as seven, the present invention may be applicable to a case of using a plurality of frequencies other than seven, and a similar effect is obtainable.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
The entire disclosure of Japanese Patent Application No. 2002-002519 filed on Jan. 9, 2002 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.
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|U.S. Classification||455/166.2, 340/928, 455/99, 340/933, 455/42, 455/41.2|
|International Classification||G07B15/00, H03J1/00, H04B1/16, H04B1/28, G08G1/09, H04B1/18|
|Cooperative Classification||H04B1/28, H03J1/0075|
|European Classification||H04B1/28, H03J1/00A5B2|
|Apr 3, 2002||AS||Assignment|
Owner name: MITSUBISHI DENKI KABUSHIKI KAISHA, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INOUE, MASAHIRO;REEL/FRAME:012761/0975
Effective date: 20020314
|Nov 18, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Jan 24, 2014||REMI||Maintenance fee reminder mailed|
|Jun 13, 2014||LAPS||Lapse for failure to pay maintenance fees|
|Aug 5, 2014||FP||Expired due to failure to pay maintenance fee|
Effective date: 20140613